Derivatives of native lignin from annual fibre feedstocks

ABSTRACT

The present invention provides derivatives of native lignin having certain aliphatic hydroxyl content. Surprisingly, it has been found that consistent and predictable antioxidant activity may be provided by selecting for derivatives of native lignin having certain aliphatic hydroxyl content.

This application is a continuation application of U.S. application Ser.No. 12/705,939, filed Feb. 15, 2010, which claims the benefit of U.S.Provisional Application Nos. 61/233,345, filed Aug. 12, 2009; and61/182,044, filed May 28, 2009. The contents of the above-identifiedapplications are incorporated herein by reference in their entirety.

FIELD

This invention relates to derivatives of native lignin recovered fromlignocellulosic feedstocks, and industrial applications thereof. Moreparticularly, this invention relates to derivatives of native ligninhaving certain chemical properties as well as uses, processes, methods,and compositions thereof.

BACKGROUND

Native lignin is a naturally occurring amorphous complex cross-linkedorganic macromolecule that comprises an integral component of all plantbiomass. The chemical structure of lignin is irregular in the sense thatdifferent structural units (e.g., phenylpropane units) are not linked toeach other in any systematic order. It is known that native lignincomprises pluralities of two monolignol monomers that are methoxylatedto various degrees (trans-coniferyl alcohol and trans-sinapyl alcohol)and a third non-methoxylated monolignol (trans-p-coumaryl alcohol).Various combinations of these monolignols comprise three building blocksof phenylpropanoid structures i.e. guaiacyl monolignol, syringylmonolignol and p-hydroxyphenyl monolignol, respectively, that arepolymerized via specific linkages to form the native ligninmacromolecule. Extracting native lignin from lignocellulosic biomassduring pulping generally results in lignin fragmentation into numerousmixtures of irregular components. Furthermore, the lignin fragments mayreact with any chemicals employed in the pulping process. Consequently,the generated lignin fractions can be referred to as lignin derivativesand/or technical lignins. As it is difficult to elucidate andcharacterize such complex mixture of molecules, lignin derivatives areusually described in terms of the lignocellulosic plant material used,and the methods by which they are generated and recovered fromlignocellulosic plant material, i.e. hardwood lignins, softwood lignins,and annual fibre lignins.

Native lignins are partially depolymerized during the pulping processesinto lignin fragments which dissolve in the pulping liquors andsubsequently separated from the cellulosic pulps. Post-pulping liquorscontaining lignin and polysaccharide fragments, and other extractives,are commonly referred to as “black liquors” or “spent liquors”,depending on the pulping process. Such liquors are generally considereda by-product, and it is common practice to combust them to recover someenergy value in addition to recovering the cooking chemicals. However,it is also possible to precipitate and/or recover lignin derivativesfrom these liquors. Each type of pulping process used to separatecellulosic pulps from other lignocellulosic components produces ligninderivatives that are very different in their physico-chemical,biochemical, and structural properties.

Given that lignin derivatives are available from renewable biomasssources there is an interest in using these derivatives in certainindustrial applications. For example, lignin derivatives obtained viaorganosolv extraction, such as the Alcell® process (Alcell is aregistered trademark of Lignol Innovations Ltd., Burnaby, BC, Calif.),have been used in rubber products, adhesives, resins, plastics, asphalt,cement, casting resins, agricultural products, oil-field products and asfeedstocks for the production of fine chemicals.

However, large-scale commercial application of the extracted ligninderivatives, particularly those isolated in traditional pulpingprocesses employed in the manufacture of pulp for paper production, hasbeen limited due to, for example, the inconsistency of their chemicaland functional properties. This inconsistency may, for example, be dueto changes in feedstock supplies and the particularextraction/generation/recovery conditions. These issues are furthercomplicated by the complexity of the molecular structures of ligninderivatives produced by the various extraction methods and thedifficulty in performing reliable routine analyses of the structuralconformity and integrity of recovered lignin derivatives. For instance,lignin derivatives are known to have antioxidant properties (e.g.Catignani G. L., Carter M. E., Antioxidant Properties of Lignin, Journalof Food Science, Volume 47, Issue 5, 1982, p. 1745; Pan X. et al. J.Agric. Food Chem., Vol. 54, No. 16, 2006, pp. 5806-5813) but, to date,these properties have been highly variable making the industrialapplication of lignin derivatives as an antioxidant problematic.

Thermoplastics and thermosets are used extensively for a wide variety ofpurposes. Examples of thermoplastics include classes of polyesters,polycarbonates, polylactates, polyvinyls, polystyrenes, polyamides,polyacetates, polyacrylates, polypropylene, and the like.

Polyolefins such as polyethylene and polypropylene represent a largemarket, amounting to more than 100 million metric tons annually. Duringmanufacturing, processing and use the physical and chemical propertiesof certain thermoplastics can be adversely affected by various factorssuch as exposure to heat, UV radiation, light, oxygen, mechanical stressor the presence of impurities. Clearly it is advantageous to mitigate oravoid these problems. In addition, the increase in recycling of materialhas led to an increased need to address these issues.

Degradation caused by free radicals, exposure to UV radiation, heat,light, and environmental pollutants are frequent causes of the adverseeffects. A stabilizer such as an antioxidant, anti-ozonant, or UV blockis often included in thermoplastic resins for the purpose of aiding inthe production process and extending the useful life of the product.Common examples of stabilizers and antioxidants include amine types,phenolic types, phenol alkanes, phosphites, and the like. Theseadditives often have undesirable or even unacceptable environmental,health and safety, economic, and/or disposal issues associated withtheir use. Furthermore, certain of these stabilizers/antioxidants canreduce the biodegradability of the product.

It has been suggested that lignin may provide a suitable polymericnatural antioxidant which has an acceptable good toxicity, efficacy, andenvironmental profile. See, for example, A. Gregorova et al., Radicalscavenging capacity of lignin and its effect on processing stabilizationof virgin and recycled polypropylene, Journal of Applied Polymer Science106-3 (2007) pp. 1626-1631; C. Pouteau et al. Antioxidant Properties ofLignin in Polypropylene, Polymer Degradation and Stability 81 (2003)9-18. Despite the advantages of lignin, for a variety of reasons, it hasnot been adopted for widespread use as an antioxidant. For instance, itis often problematic to provide lignins that perform consistently interms of antioxidant activity. Also, the processing of the lignin mayintroduce substances that are incompatible for use with chemicals suchas polyolefins. Additionally, the cost of producing and/or purifying thelignin may make it uneconomic for certain uses.

SUMMARY

The present invention provides derivatives of native lignin having acertain aliphatic hydroxyl content. Surprisingly, it has been found thatconsistent and predictable antioxidant activity may be provided byselecting for derivatives of native lignin having certain aliphatichydroxyl contents.

As used herein, the term “native lignin” refers to lignin in its naturalstate, in plant material.

As used herein, the terms “lignin derivatives” and “derivatives ofnative lignin” refer to lignin material extracted from lignocellulosicbiomass. Usually, such material will be a mixture of chemical compoundsthat are generated during the extraction process.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 shows the quantitative ¹³C NMR spectrum of non-acetylatedsugarcane bagasse lignin derivatives.

FIG. 2 shows the quantitative ¹³C NMR spectrum of acetylated sugarcanebagasse lignin derivatives.

DETAILED DESCRIPTION

The present invention provides derivatives of native lignin from annualfeedstocks having certain aliphatic hydroxyl contents. It has been foundthat the aliphatic hydroxyl content of lignin derivatives can becorrelated to the Radical Scavenging Index (RSI), a measure ofantioxidant activity. Thus, selecting for derivatives of native ligninhaving a certain aliphatic hydroxyl content results in a product havinga more consistent level of antioxidant activity. It has been found thatderivatives of native lignin from annual feedstocks having an aliphatichydroxyl content of about 1 mmol/g to about 3.75 mmol/g have apredictable level of antioxidant activity.

Radical Scavenging Index (RSI) is a measure of radical scavengingcapacity. The assay uses 2,2-diphenyl-1-picrylhydrazyl (DPPH), a stablefree radical which absorbs light strongly at 515 nm, to measure acompound's radical scavenging index (RSI). In its radical form, DPPH•absorbs strongly at 515 nm and has a deep purple colour. As DPPH givesup its free electron to radical scavengers, it loses its purple colourand its absorbance shifts to 520 nm. The greater the drop in DPPHabsorbance at 515 nm after a test compound has been added to the DPPHsolution, the higher the compound's free RSI and also, its antioxidantactivity. In the present invention, Vitamin E (Vit. E) and butylatedhydroxytoluene (BHT) are used as positive controls. The ligninderivative samples (1.0-2.0 mg), Vit. E control samples (1.0-2.0 mg),and BHT control samples (6.0-8.0 mg) are prepared for testing by beingplaced into microcentrifuge tubes after which each was diluted with 1.0mL of 90% (v/v) aqueous dioxan, vortexed, transferred to newmicrocentrifuge tubes and further diluted 50/50 with 90% aqueous dioxaneto give stock concentrations of 0.5-1.0 mg/mL for samples and Vitamin Eand 3.0-4.0 mg/mL for BHT. An indicating (purple) DPPH stable freeradical solution is made by dissolving 3.78 mg DPPH in 100 mL 90%dioxane (95.9 μM). Samples and standards are serially diluted to fillcolumns of a quartz 96-well plate (8 dilutions). The assays areperformed by placing aliquots of the sample stock solutions into tworows of wells in a 96-well plate. The first row served as the referencerow while the second row received DPPH aliquots. 165 μL of 90% dioxanewas added to each well and mixed. Aliquots of the mixed samples in eachrow are transferred to the adjacent row which is further diluted with165 μL of 90% dioxane in each well. The mixing, transferring anddilution are repeated until the last row of wells is prepared. The samevolume of aliquots is removed from the last row. The 96-well plate alsocontains a row of wells that received only the 90% dioxane. In the finalstep of the preparation procedure, 165 μL of the DPPH solution is addedas quickly as possible to all the control and analytical columns byusing an 8-channel auto-pipette and an Eppendorf® reagent reservoir. Assoon as all reagents are added, the plate is placed into a plate-readingspectrophotometer (Spectra Max Plus, Molecular Devices, Sunnyvale,Calif., USA), and absorbance measurements are carried out. The programfor the spectrophotometer (SOFTmax software) consists of a timingsequence of 16 min and a reading of the entire plate at 515 nm. RSI isdefined as the inverse of the concentration which produces 50%inhibition in DPPH absorbance at 515 nm. The results are then‘normalized’ by dividing the sample RSI by the RSI value for the BHTcontrol. The normalized RSI is represented by this acronym “NRSI”.

In the present invention, “aliphatic hydroxyl content” refers to thequantity of aliphatic hydroxyl groups in the lignin derivatives and isthe arithmetic sum of the quantity of primary and secondary hydroxylgroups (OHal=OHpr+OHsec). The aliphatic hydroxyl content can be measuredby quantitative ¹³C high resolution NMR spectroscopy of acetylated andnon-acetylated lignin derivatives, using, for instance, 1,3,5-trioxaneand tetramethyl silane (TMS) as internal references. For the dataanalysis “BASEOPT” (DIGMOD set to baseopt) routine in the softwarepackage TopSpin 2.1.4 was used to predict the first FID data point backat the mid-point of ¹³C r.f. pulse in the digitally filtered data wasused. For the NMR spectra recording a Bruker AVANCE II digital NMRspectrometer running TopSpin 2.1 was used. The spectrometer used aBruker 54 mm bore Ultrashield magnet operating at 14.1 Tesla (600.13 MHzfor ¹H, 150.90 MHz for ¹³C). The spectrometer was coupled with a BrukerQNP cryoprobe (5 mm NMR samples, ¹³C direct observe on inner coil, ¹Houter coil) that had both coils cooled by helium gas to 20K and allpreamplifiers cooled to 77K for maximum sensitivity. Sample temperaturewas maintained at 300 K±0.1 K using a Bruker BVT 3000 temperature unitand a Bruker BCUO5 cooler with ca. 95% nitrogen gas flowing over thesample tube at a rate of 800 L/h.

Quantification of ethoxyl groups was performed similarly to aliphatichydroxyls quantification by high resolution ¹³C NMR spectroscopy.Identification of ethoxyl groups was confirmed by 2D NMR HSQCspectroscopy. 2D NMR spectra were recorded by a Bruker 700 MHzUltraShield Plus standard bore magnet spectrometer equipped with asensitive cryogenically cooled 5mm TCI gradient probe with inversegeometry. The acquisition parameters were as follow: standard Brukerpulse program hsqcetgp, temperature of 298 K, a 90° pulse, 1.1 sec pulsedelay (dl), and acquisition time of 60 msec.

The present invention provides derivatives of native lignin recoveredduring or after pulping of lignocellulosic feedstocks. The pulp may befrom any suitable lignocellulosic feedstock such as from annual fibrefeedstocks. Annual fibre feedstocks include biomass derived from annualplants, plants which complete their growth in one growing season andtherefore must be planted yearly. Examples of annual fibers include:flax, cereal straw (wheat, barley, oats), sugarcane bagasse, rice straw,corn stover, corn cobs, hemp, fruit pulp, alfa grass, switchgrass, andcombinations/hybrids thereof. Industrial residues like corn cobs, fruitpeals, seeds, etc. may also be considered annual fibers since they arecommonly derived from annual fibre biomass such as edible crops andfruits. For example, the annual fibre feedstock may be selected fromwheat straw, corn stover, corn cobs, sugar cane bagasse, andcombinations/hybrids thereof.

Derivatives of native lignin according to the present invention, comingfrom annual fibre feedstocks tend to have a NRSI of about 100 or less,about 90 or less, about 80 or less, about 70 or less, about 60 or less.

In the present invention, derivatives of native lignin from annual fibrefeedstocks may have an aliphatic hydroxyl content of, for example, about3.75 mmol/g or less; about 3.5 mmol/g or less; about 3.25 mmol/g orless; about 3 mmol/g or less; about 2.75 mmol/g or less; about 2.5mmol/g or less; about 2.35 mmol/g or less; about 2.25 mmol/g or less.

In the present invention, derivatives of native lignin from annual fibrefeedstocks may have an aliphatic hydroxyl content of, for example, about1 mmol/g or greater; about 1.1 mmol/g or greater; about 1.2 mmol/g orgreater; about 1.3 mmol/g or greater; about 1.4 mmol/g or greater; about1.5 mmol/g or greater.

The derivatives of native lignin will vary with the type of process usedto separate native lignins from cellulose and other biomassconstituents. Preparations very similar to native lignin can be obtainedby (1) solvent extraction of finely ground wood (milled-wood lignin,MWL) or by (2) acidic dioxane extraction (acidolysis) of wood.Derivatives of native lignin can be also isolated from biomasspre-treated using (3) steam explosion, (4) dilute acid hydrolysis, (5)ammonia fibre expansion, (6) autohydrolysis methods. Derivatives ofnative lignin can be recovered after pulping of lignocellulosicsincluding industrially operated (3) kraft and (4) soda pulping (andtheir modifications) and (5) sulphite pulping. In addition, a number ofvarious pulping methods have been developed but not industriallyintroduced. Among them four major “organosolv” pulping methods tend toproduce highly-purified lignin mixtures. The first organosolv methoduses ethanol/solvent pulping (aka the Alcell® process); the secondorganosolv method uses alkaline sulphite anthraquinone methanol pulping(aka the “ASAM” process); the third organosolv process uses methanolpulping followed by methanol, NaOH, and anthraquinone pulping (aka the“Organocell” process); the fourth organosolv process uses aceticacid/hydrochloric acid or formic acid pulping (aka the “Acetosolv”process).

It should be noted that kraft pulping, sulphite pulping, and ASAMorganosolv pulping will generate derivatives of native lignin containingsignificant amounts of organically-bound sulphur which may make themunsuitable for certain uses. Acid hydrolysis, soda pulping, steamexplosion, Alcell® pulping, Organocell pulping, and Acetosolv pulpingwill generate derivatives of native lignin that are sulphur-free orcontain low amounts of inorganic sulphur.

Organosolv processes, particularly the Alcell® process, tend to be lessaggressive and can be used to separate highly purified ligninderivatives and other useful materials from biomass without excessivelyaltering or damaging the native lignin building blocks. Such processescan therefore be used to maximize the value from all the componentsmaking up the biomass. Organosolv extraction processes however typicallyinvolve extraction at higher temperatures and pressures with a flammablesolvent compared to other industrial processes and thus are generallyconsidered to be more complex and expensive.

A description of the Alcell® process can be found in US Patent 4,764,596(herein incorporated by reference). The process generally comprisespulping or pre-treating a fibrous biomass feedstock with primarily anethanol/water solvent solution under conditions that include: (a) 60%ethanol/40% water (w/w), (b) temperature of about 180° C. to about 210°C., (c) pressure of about 20 atm to about 35 atm, and (d) a processingtime of 5 to 120 minutes. Native lignins are degraded during pulping andtheir derivatives are dissolved into the pulping liquor which alsoreceives solubilised hemicelluloses, other saccharides,carbohydrate-degradation products such as furfural, 5-hydroxymethylfurfural, acetic, levulinic, formic, and other organic acids derivedfrom carbohydrates and extractives such as lipophilic extractives,phenols, and tannins. Organosolv pulping liquors are often called “blackliquors”. The organic acids released by organosolv pulping significantlyacidify the black liquors to pH levels of about 5 and lower. Afterseparation from the cellulosic pulps produced during the pulpingprocess, the derivatives of native lignin are recovered from the blackliquors by depressurization followed by flashing with cold water whichwill cause the fractionated derivatives of native lignin to precipitatethereby enabling their recovery by standard solids/liquids separationprocesses. Various disclosures exemplified by U.S. Pat. No. 7,465,791and PCT Patent Application Publication No. WO 2007/129921, describemodifications to the Alcell organosolv process for the purposes ofincreasing the yields of fractionated derivatives of native ligninrecovered from fibrous biomass feedstocks during biorefining.Modifications to the Alcell organosolv process conditions includedadjusting: (a) ethanol concentration in the pulping liquor to a valueselected from a range of 35%-85% (w/w) ethanol, (b) temperature to avalue selected from a range of 100° C. to 350° C., (c) pressure to avalue selected from a range of 5 atm to 35 atm, and (d) processing timeto a duration from a range of 20 minutes to about 2 hours or longer, (e)liquor-to-wood ratio of 3:1 to 15:1 or higher, (f) pH of the cookingliquor from a range of 1 to 6.5 or higher if a basic catalyst is used.

The present invention provides a process for producing derivatives ofnative lignin, said process comprising:

(a) pulping a fibrous biomass feedstock with an organic solvent/watersolution,

(b) separating the cellulosic pulps or pre-treated substrates from thepulping liquor or pre-treatment solution,

(c) recovering derivatives of native lignin.

The organic solvent may be selected from short chain primary andsecondary alcohols, such as methanol, ethanol, propanol, andcombinations thereof. For example, the solvent may be ethanol. Theliquor solution may comprise about 20%, by weight, or greater, about 30%or greater, about 50% or greater, about 60% or greater, about 70% orgreater, of ethanol.

Step (a) of the process may be carried out at a temperature of fromabout 100° C. and greater, or about 120° C. and greater, or about 140°C. and greater, or about 160° C. and greater, or about 170° C. andgreater, or about 180° C. and greater. The process may be carried out ata temperature of from about 300° C. and less, or about 280° C. and less,or about 260° C. and less, or about 240° C. and less, or about 220° C.and less, or about 210° C. and less, or about 205° C. and less, or about200° C. and less.

Step (a) of the process may be carried out at a pressure of about 5 atmand greater, or about 10 atm and greater, or about 15 atm and greater,or about 20 atm and greater, or about 25 atm and greater, or about 30atm and greater. The process may be carried out at a pressure of about150 atm and less, or about 125 atm and less, or about 115 atm and less,or about 100 atm and less, or about 90 atm and less, or about 80 atm andless.

The fibrous biomass may be treated with the solvent solution of step (a)for about 1 minute or more, about 5 minutes or more, about 10 minutes ormore, about 15 minutes or more, about 30 minutes or more. The fibrousbiomass may be treated with the solvent solution of step (a) at itsoperating temperature for about 360 minutes or less, about 300 minutesor less, about 240 minutes or less, about 180 minutes or less, about 120minutes or less.

The pH of the pulp liquor may, for example, be from about 1 to about 6,or from about 1.5 to about 5.5.

The weight ratio of liquor to biomass may be any suitable ratio. Forexample, from about 5:1 to about 15:1, from about 5.5:1 to about 10:1;from about 6:1 to about 8:1.

The present invention provides a process for producing a ligninderivative from an annual fibre feedstock having an aliphatic hydroxylcontent of from about 1 mmol/g to about 3.75 mmol/g. Said processcomprises:

a) pulping or pre-treating a fibrous biomass feedstock in a vessel withan organic solvent/water solvent solution to form a liquor, wherein:

-   -   i. the solution comprises about 30% or greater, by weight, of        organic solvent; and    -   ii. the pH of the liquor is from about 1 to about 5.5;        b) heating the liquor to about 100° C. or greater;        c) raising the pressure in the vessel to about 5 atm or greater;        d) maintaining the elevated temperature and pressure for 1        minute or longer;        e) separating the cellulosic pulps from the pulp liquor        f) recovering derivatives of native lignin.

The derivatives of native lignin herein may be incorporated into polymercompositions. The compositions herein may comprise a lignin derivativeaccording to the present invention and a polymer-forming component. Asused herein, the term ‘polymer-forming component’ means a component thatis capable of being polymerized into a polymer as well as a polymer thathas already been formed. For example, in certain embodiments thepolymer-forming component may comprise monomer units which are capableof being polymerized. In certain embodiments the polymer component maycomprise oligomer units that are capable of being polymerized. Incertain embodiments the polymer component may comprise a polymer that isalready substantially polymerized.

Polymers forming components for use herein may result in thermoplasticor thermoset polymers such as epoxy resins, urea-formaldehyde resins,phenol-formaldehyde resins, polyimides, and the like. For example,polyalkenes such as polyethylene or polypropylene.

Typically, the lignin derivative will comprise from about 0.1%, byweight, or greater, about 0.5% or greater, about 1% or greater, of thecomposition. Typically, the lignin derivative will comprise from about80%, by weight, or less, about 60% or less, about 40% or less, about 20%or less, about 10% or less, of the composition.

The compositions comprise lignin derivative and polymer-formingcomponent but may comprise a variety of other optional ingredients suchas adhesion promoters; biocides (antibacterials, fungicides, andmoldicides), anti-fogging agents; anti-static agents; bonding, blowingand foaming agents; dispersants; fillers and extenders; fire and flameretardants and smoke suppressants; impact modifiers; initiators;lubricants; micas; pigments, colorants and dyes; plasticizers;processing aids; release agents; silanes, titanates and zirconates; slipand anti-blocking agents; stabilizers; stearates; ultraviolet lightabsorbers; foaming agents; defoamers; hardeners; odorants; deodorants;antifouling agents; viscosity regulators; waxes; and combinationsthereof.

The present invention provides the use of the present derivatives ofnative lignin as an antioxidant. For example, the present use may be asan antioxidant additive for use with thermoplastic polymers such aspolyethylene, polypropylene, polyamides, styrene-butadiene, naturalrubber, and combinations thereof.

The present invention provides methods of producing annual fibrederivatives of native lignin having an aliphatic hydroxyl content ofabout 3.75 mmol/g or less; 3.5 mmol/g or less; 3.25 mmol/g or less; 3mmol/g or less; 2.75 mmol/g or less; 2.5 mmol/g or less; 2.35 mmol/g orless; 2.25 mmol/g or less. The present invention provides methods ofproducing annual fibre derivatives of native lignin having an aliphatichydroxyl content of about 1 mmol/g or greater; about 1.1 mmol/g orgreater; about 1.2 mmol/g or greater; about 1.3 mmol/g or greater; about1.4 mmol/g or greater; about 1.5 mmol/g or greater.

The present invention provides methods of producing annual fibrederivatives of native lignin having a normalized RSI of 15 or greater,20 or greater, 25 or greater, 30 or greater, 35 or greater. The presentinvention provides methods of producing annual fibre derivatives ofnative lignin having a normalized RSI of about 100 or less, about 90 orless, about 80 or less, about 70 or less, about 60 or less.

The present invention provides lignin derivatives comprising alkoxygroups. For example, the present lignin derivatives may have an alkoxycontent of 2 mmol/g or less; about 1.4 mmol/g or less; about 1.2 mmol/gor less; about 1 mmol/g or less; about 0.8 mmol/g or less; about 0.7mmol/g or less; about 0.6 mmol/g or less; about 0.5 mmol/g or less;about 0.4 mmol/g or less; about 0.3 mmol/g or less. The present ligninderivatives may have an alkoxy content of 0.001 mmol/g or greater, about0.01 mmol/g of greater, about 0.05 mmol/g or greater, about 0.1 mmol/gor greater.

The present invention provides lignin derivatives comprising ethoxylgroups. For example, the present lignin derivatives may have an ethoxylcontent of 2 mmol/g or less; about 1.4 mmol/g or less; about 1.2 mmol/gor less; about 1 mmol/g or less; about 0.8 mmol/g or less; about 0.7mmol/g or less; about 0.6 mmol/g or less; about 0.5 mmol/g or less;about 0.4 mmol/g or less; about 0.3 mmol/g or less. The present ligninderivatives may have an ethoxyl content of 0.001 mmol/g or greater,about 0.01 mmol/g of greater, about 0.05 mmol/g or greater, about 0.1mmol/g or greater.

The present lignin derivatives may have any suitable phenolic hydroxylcontent such as from about 2 mmol/g to about 8 mmol/g. For example, thephenolic hydroxyl content may be from about 2.5 mmol/g to about 7mmol/g; about 3 mmol/g to about 6 mmol/g.

The present lignin derivatives may have any suitable number averagemolecular weight (Mn). For example, the Mn may be from about 200 g/molto about 3000 g/mol; about 350 g/mol to about 2000 g/mol; about 500g/mol to about 1500 g/mol.

The present lignin derivatives may have any suitable weight averagemolecular weight (Mw). For example, the Mw may be from about 500 g/molto about 5000 g/mol; about 750 g/mol to about 4000 g/mol; about 900g/mol to about 3500 g/mol.

The present lignin derivatives may have any suitable polydispersity (D).For example, the D may be from about 1 to about 5; from about 1.2 toabout 4; from about 1.3 to about 3.5; from about 1.4 to about 3.

The present lignin derivatives are preferably hydrophobic.Hydrophobicity may be assessed using contact angle measurements.

It has been suggested that lignins or lignin derivatives may be used innutritional supplements (e.g. Baurhoo et. al., Purified Lignin:Nutritional and Health Impacts on Farm Animals—A Review, Animal FeedScience and Technology 144 (2008) 175-184). The present derivatives ofnative lignin may be used in nutritional supplements, nutraceuticals,functional foods, and the like. The stable and consistent antioxidantactivity may be advantageous when formulating such compositions.

The present derivatives of native lignin may be used for other purposessuch as, for example, laminates, stains, pigments, inks, adhesives,coatings, rubbers, elastomers, plastics, films, paints, carbon fibrecomposites, panel boards, print-circuit boards, lubricants, surfactants,oils, animal feed, food and beverages, and the like.

EXAMPLES Example 1 Recovery of Lignin Derivatives From Annual FibreFeedstocks

Annual fibre feedstock pretreated biomass was prepared from: (1) wheatstraw produced in Alberta, Canada, (2) bagasse produced from sugarcanegrown and processed in Brazil, and (3) corn cobs produced in Europe.Five samples of wheat straw biomass were individually pulped using anacid-catalysed ethanol organosolv pulping process wherein a differentset of pulping conditions was used for each sample (Table 1). Processconditions for pulping five samples of sugarcane bagasse biomass areshown in Table 2. Process conditions for pulping five samples ofshredded corn cob biomass are shown in Table 3.

TABLE 1 Pulping conditions for wheat straw biomass samples at 6:1liquor-to-wood ratio. Time Temperature Run pH Acid % min ° C. Ethanol %PL % 1 2.86 0.30 90 195 41 38.17 2 2.26 0.90 49 192 37 37.01 3 2.24 2.0048 184 65 43.48 4 2.03 2.00 77 176 42 40.81 5 2.45 1.00 79 178 49 39.27

TABLE 2 Pulping conditions for sugarcane bagasse biomass samples at 6:1liquor-to-wood ratio. Time Temperature Run pH Acid % min ° C. Ethanol %PL % 1 2.19 2.50 61 178 66 49.76 2 2.01 3.00 23 170 66 39.56 3 2.19 2.0054 164 58 44.95 4 2.93 0.40 69 184 42 30.26 5 3.26 0.30 32 197 51 42.14

TABLE 3 Pulping conditions for corn cob biomass samples at 6:1liquor-to-wood ratio. Time Temperature Run pH Acid % min ° C. Ethanol %PL % 1 2.18 2.20 100 190 67 56.58 2 2.21 2.00 48 184 65 49.62 3 2.111.50 106 176 38 32.28 4 2.31 1.30 94 178 61 47.72 5 2.50 0.70 59 182 4537.77

For each biomass sample, the ethanol pulping solvent was prepared to thespecified concentration by first, partially diluting the ethanol withwater after which, a suitable amount of sulphuric acid was added toachieve the target final acidity. Finally, the ethanol solution wasfurther diluted with water to achieve the target ethanol concentration.

The original lignin content of each fibrous biomass subsample wasdetermined using the methods described in the National Renewable EnergyLaboratory (NREL) Technical Report entitled “Determination of StructuralCarbohydrates and Lignin in Biomass”—Laboratory Analytical Procedure(TP-510-42618 (25 Apr. 2008)). Then, after adding the fibrous biomasssample to a pressure vessel (2L or 7 L Parr reactor (Parr InstrumentCompany, Moline, Ill., USA)) (100-700 g odw chips), the pH-adjustedethanol-based pulping solvent was added to the vessel at a 6:1liquor:wood ratio & the pH recorded. The vessel was then pressurized andbrought up to the target temperature listed in Tables 1-3 (wheat straw,bagasse, corn cobs, respectively). The biomass sample was then “cooked”for the specified period of time, after which, the pulping process wasstopped. After pulping, the contents of pressure vessel were transferredto a hydraulic 20 ton manual shop press (Airco, China). The liquor wasseparated from the solids by first squeezing the pulped materials in thepress to express the liquor. The expressed liquor was then filteredthrough a coarse silk screen to separate expressed chip residues fromliquor stream. Next, fine particles were separated out from the liquorstream by filtration through fine filter paper (Whatman N° 1). Therecovered fine particles represent lignin derivatives that wereextracted and self-precipitated out from the liquor during cooling ofthe pulped biomass. The particulate lignin is herein referred to asself-precipitated lignin derivatives (i.e., “SPL”). The solubilizedlignin derivatives still remaining in the filtered liquor wereprecipitated from by dilution with cold water. The lignin derivativesprecipitated by dilution with cold water are referred to as precipitatedlignin or “PL”. After determination of the dry weights of SPL and PLlignin derivatives, the relative yield of each lignin derivative wasdetermined in reference to total lignin (sum of the Klason lignin(acid-insoluble lignin) and acid-soluble lignin) value determined forthe original biomass sample before pulping. The yield of PL ligninderivatives for each sample is shown in Tables 1-3 on a weight % basisrelative to their original lignin (Klason plus acid-soluble ligninvalues).

Example 2 Characterization of the aliphatic hydroxyl content of ligninderivatives recovered from three annual fibre species

Functionalized lignin derivatives recovered from annual fibre biomasssamples as described above, were analyzed to determine the content ofprimary hydroxyl groups mmol/g sample (OH-pr mmol/g) and content ofsecondary hydroxyl groups mmol/g sample (OH-sec mmol/g). These valueswere then used to calculate mmol aliphatic hydroxyl groups/g sample(OH-al mmol/g).

The hydroxyl contents were determined by quantitative ¹³C NMRspectroscopy on a Bruker 600 MHz spectrometer equipped with Cryoprobe at300 K using ca 30% solutions of sample in DMSO-d₆. Chemical shifts werereferenced to TMS (0.0 ppm). To ensure more accurate baseline,especially in the carbonyl region (215-185 ppm), the spectra wererecorded in the interval 240-(-40) ppm. The following conditions wereprovided for the quantitative ¹³C-NMR:

1. Inverse gate detection;2. a 90° pulse;3. Complete relaxation of all nuclei was achieved by addition ofchromium (III) acetylacetonate (0.01 M) and using a 1.2 s acquisitiontime and 1.7 s relaxation delay acquisition parameters.

The NMR spectra were Fourier-transformed, phased, calibrated using TMSsignals as a reference (0 ppm), and the baseline was corrected by usinga polynomial function. The correction of baseline was done using thefollowing interval references to be adjusted to zero: (220-225ppm)-(185-182 ppm)-(97-92 ppm)-(5-(-20)ppm). No other regions wereforced to 0. The signals in the quantitative ¹³C NMR spectra wereassigned on the basis of 2D HSQC spectra and a known database. Thespectra were integrated then using the area of internal standard (IS),trioxane, as the reference. Each spectrum was processed (as described)at least twice to ensure good reproducibility of the quantification.Some carboxyl and ester groups resonate in the resonance area ofhydroxyl groups (171.5-166.5 ppm) in the spectra of acetylated lignins.The amounts of carboxyl and ester groups resonated in the interval of171.5-166.5 ppm were determined from the spectra of non-acetylatedlignins. The corrected content of hydroxyl groups was obtained then bydeduction of the amounts of the carboxyl and ester groups from thecorresponding resonances of hydroxyl groups (Table 4). The calculationof the quantity of the specific moieties was done as follows:

For non-acetylated lignins:

X(mmol/g lignin)=I _(x) *m _(IS)/(30m _(Lig) *I _(IS))*1000

For acetylated lignins:

X(mmol/g lignin)=I _(x) *m _(IS)/(30m _(Lig) *I _(IS)−42I _(OHtotal) *m_(IS))*1000

Where X was the amount of the specific moiety; I_(X), I_(IS) andI_(OHtotal) were the resonance values of the specific moiety (Table 4),the internal standard and total OH groups, correspondingly; m_(Lig) andm_(Lig) are the masses of the lignin and internal standard.

The recorded NMR spectroscopic data are processed and graphicallyillustrated as shown in FIGS. 1 and 2. FIG. 1 shows quantitative ¹³C NMRspectrum of non-acetylated sugarcane bagasse lignin derivatives. FIG. 2shows quantitative ¹³C NMR spectrum of acetylated sugarcane bagasselignin derivatives

TABLE 4 Symbol I_(X) in Calculation Equation Analytical Method OH-prResonance at 171.5-169.7 ppm in the Quantitative ¹³C High Resolution NMRof mmol/g quantitative ¹³C NMR spectra of lignin using 1,3,5-trioxane asinternal acetylated lignins minus resonance at reference 171.5-169.7 ppmin the quantitative ¹³C NMR spectra of non-acetylated lignins OH-secResonance at 169.7-169.2 ppm in the Quantitative ¹³C High Resolution NMRof mmol/g quantitative ¹³C NMR spectra of lignin using 1,3,5-trioxane asinternal acetylated lignins minus resonance at reference 169.7-169.2 ppmin the quantitative ¹³C NMR spectra of non-acetylated lignins OH-Resonance at 171.5-165.0 ppm in the Quantitative ¹³C High Resolution NMRof total quantitative ¹³C NMR spectra of lignin using 1,3,5-trioxane asinternal mmol/g acetylated lignins minus resonance at reference171.5-166.5 ppm in the quantitative ¹³C NMR spectra of non-acetylatedlignins OH-al OH-al = OH-pr + OH-sec mmol/g OEt Resonance at 16.0-14.5ppm in the Quantitative ¹³C High Resolution NMR of mmol/g quantitative¹³C NMR spectra (both lignin using 1,3,5-trioxane as internal inacetylated and non-acetylated reference combined with 2D ¹H-¹³C NMRlignins, calculated as average)

The aliphatic hydroxyl contents of the PL lignin derivatives from eachof the five samples of wheat straw biomass are shown in Table 5. Thecontents ranged from 2.03 mmol/g in sample 1.00 to 3.36 mmol/g in sample5.

TABLE 5 Aliphatic hydroxyl content and radical scavenging index of PLlignins recovered from wheat straw biomass. OH-pr OH-sec OH-al Runmmol/g mmol/g mmol/g NRSI 1 1.20 0.82 2.03 54.03 2 1.36 1.10 2.47 55.323 1.67 1.15 2.82 36.63 4 1.66 1.42 3.08 42.18 5 1.80 1.56 3.36 36.82

The aliphatic hydroxyl contents of the PL lignin derivatives from eachof the five samples of sugarcane bagasse biomass are shown in Table 6.The contents ranged from 1.74 mmol/g in sample 1 to 2.92 mmol/g insample 5.

TABLE 6 Aliphatic hydroxyl content and radical scavenging index of PLlignins recovered from sugarcane bagasse biomass. OH-pr OH-sec OH-al Runmmol/g mmol/g mmol/g NRSI 1 1.02 0.73 1.74 52.34 2 1.19 0.89 2.09 41.803 1.31 1.02 2.34 38.74 4 1.47 1.05 2.51 37.80 5 1.53 1.39 2.92 39.05

The aliphatic hydroxyl contents of the PL lignin derivatives from eachof the four samples of corn cob biomass are shown in Table 7. Thecontents ranged from 1.58 mmol/g in sample 1 to 3.16 mmol/g in sample 5.

TABLE 7 Aliphatic hydroxyl content and radical scavenging index of PLlignins recovered from corn cob biomass. OH-pr OH-sec OH-al Run mmol/gmmol/g mmol/g NRSI 1 0.95 0.63 1.58 45.15 2 0.50 1.62 2.12 40.34 3 0.821.58 2.39 42.20 4 0.80 1.97 2.77 38.30 5 1.37 1.79 3.16 51.41

Example 3 Characterization of the NRSI of Lignin Derivatives RecoveredFrom Three Annual Fibre Species

The lignin derivatives samples produced above were assessed for theirradical scavenging index (RSI). The potential antioxidant activity ofeach PL lignin derivative was determined by measuring its radicalsavaging capacity. The assay used 2,2-diphenyl-1-picrylhydrazyl (DPPH),a stabile free radical which absorbs light strongly at 515 nm to measurea compound's radical scavenging index (RSI). In its radical form, DPPH•absorbs strongly at 515 nm and has a deep purple colour. As DPPH givesup its free electron to radical scavengers, it loses its purple colourand its absorbance shifts to 520 nm. The greater the drop in DPPHabsorbance at 515 nm after a test compound has been added to the DPPHsolution, the higher the compound's free RSI and also, its antioxidantactivity. In the present study, Vit. E and BHT were used as positivecontrols. HPLY lignin derivative subsamples (1.0-2.0 mg), Vit. E controlsamples (1.0-2.0 mg), and BHT control samples (6.0-8.0 mg) were preparedfor testing by being placed into epitubes after which, each was dilutedwith 1.0 mL of 90% (v/v) aqueous dioxan, vortexed, transferred to newepitubes and then further diluted 50/50 with 90% aqueous dioxane to givestock concentrations of 0.5-1.0 mg/mL for samples and Vitamin E and3.0-4.0 mg/mL for BHT. An indicating (purple) DPPH stable free radicalsolution is made by dissolving 3.78 mg DPPH in 100 mL 90% dioxane (95.9μM). Samples and standards are serial diluted to fill columns of aquartz 96-well plate (8 dilutions). The assays were performed by placingaliquots of the sample stock solutions into two rows of wells in a96-well plate. The first row served as the reference row while thesecond row received DPPH aliquots. 165 μL of 90% dioxane was added toeach well and mixed. Aliquots of the mixed samples in each row weretransferred to the adjacent row and further diluted with 165 μL of 90%dioxane in each well. The mixing, transferring and dilution wererepeated until the last row of wells is prepared. The same volume ofaliquots was removed from the last row. The 96-well plate also containeda row of wells that received only the 90% dioxane.

In the final step of the preparation procedure, 165 μL of the DPPHsolution was added to all the control and analytical columns by using an8-channel auto-pipette and an Eppendorf® reagent reservoir as quickly aspossible. As soon as all reagents are added, the plate is placed into aplate-reading spectrophotometer (Molecular Devices, Sunnyvale, Calif.,USA, Spectra Max Plus), and absorbance measurements are commenced. Theprogram for the spectrophotometer (SOFTmax software) consisted of atiming sequence of 16 min and a reading of the entire plate at 515 nm.RSI (radical scavenging index) is defined as the inverse of theconcentration which that produced 50% inhibition in DPPH absorbance at515 nm. The results were then ‘normalized’ (NRSI) by dividing the sampleRSI by the RSI value for the BHT control.

The NRSI values for lignin derivatives recovered from wheat strawbiomass are shown in Table 5. The NRSI values for lignin derivativesrecovered from sugarcane bagasse biomass are shown in Table 6. The NRSIvalues for lignin derivatives recovered from corn cob biomass are shownin Table 7.

What is claimed is:
 1. A thermoplastic composition comprising an annualfibre lignin derivative, wherein said lignin derivative has an aliphatichydroxyl content of from about 1 mmol/g to about 3.75 mmol/g and anormalized RSI of 15 or greater.
 2. The composition according to claim1, wherein the derivative has an aliphatic hydroxyl content is fromabout 1 mmol/g to about 3.25 mmol/g.
 3. The composition according toclaim 1, wherein the derivative comprises ethoxyl groups.
 4. Thecomposition according to claim 3, wherein the ethoxyl content is 1.4mmol/g or less.
 5. The composition according to claim 1, wherein thederivative has an aliphatic hydroxyl content is from about 1 mmol/g toabout 3.25 mmol/g.
 6. The composition according to claim 1, wherein thederivative comprises ethoxyl groups.
 7. The composition according toclaim 7, wherein the ethoxyl content is 1.4 mmol/g or less.
 8. Apolyolefin composition comprising an annual fibre lignin derivative,wherein said lignin derivative has an aliphatic hydroxyl content of fromabout 1 mmol/g to about 3.75 mmol/g and a normalized RSI of 15 orgreater.
 9. A method of producing an annual fibre lignin derivative,comprising: a) pulping a fibrous biomass; b) heating the pulp; c)maintaining the elevated temperature for 1 minute or longer; d)separating the cellulosic pulp from the lignin rich pulp; and e)recovering derivatives of native lignin, wherein the derivatives have analiphatic hydroxyl content of from about 1 mmol/g to about 3.75 mmol/gand a normalized RSI of 15 or greater.
 10. The method according to claim9, wherein the pulping process is selected from the group consisting of:steam explosion, dilute acid hydrolysis, ammonia fiber expansion,autohydrolysis, kraft and modifications thereof, soda pulping andmodifications thereof, sulphite pulping, and organosolv processes. 11.The method according to claim 9, wherein the pulping process is a kraftprocess or a modification thereof.
 12. The method according to claim 9,wherein the pulping process is an organosolv process.